1. Field of the Invention
The present invention relates to isolated polypeptides having choline oxidase activity and isolated nucleic acid sequences encoding the polypeptides. The invention also relates to nucleic acid constructs, vectors, and host cells comprising the nucleic acid sequences as well as methods for producing and using the polypeptides.
2. Description of the Related Art
Choline oxidase (EC 1.1.3.17) is a bifunctional enzyme capable of catalyzing the biosynthesis of glycine betaine from choline via betaine aldehyde. The enzyme is a soluble enzyme containing a covalently attached FAD. Choline is the natural hydrolysis product of lecithin. Glycine betaine is proposed to have an osmoprotective role in a number of microorganisms and plants. Besides this physiological role as an osmoprotectant, glycine betaine functions in general metabolism where methyl groups derived from it are incorporated into alkaloids in plants, into methionine in mammals and microorganisms, and into cobalamin (vitamin B.sub.12) in microorganisms. Furthermore, betaine can be used as a carbon and nitrogen source by some microorganisms.
Choline oxidase has applications in clinical biochemistry, where choline oxidase is used for the estimation of choline-containing phospholipids in serum and amniotic fluid. Furthermore, a gene encoding choline oxidase may be suitable for enhancing osmotolerance in biological systems of interest, e.g., plants.
JP 54035284 discloses the preparation of a choline oxidase from microorganisms belonging to the genus Cylindrocarpon, Fusarium, or Gibberella.
Deschnium et al. (1995, Plant Molecular Biology 29: 897-907)disclose the cloning of a choline oxidase gene from Arthrobacter globiformis. Rozwadowski et al. (1991, Journal of Bacteriology 173: 472-478)disclose the cloning of a choline oxidase from Arthrobacter pascens. JP 5317056 discloses the cloning of a choline oxidase from Thermoactinomyces monosporus.
It is an object of the present invention to provide improved polypeptides having choline oxidase activity and nucleic acids encoding the polypeptides.